Oil circuit breakers



Aug. 9, 1960 H. FORWALD on CIRCUIT BREAKERS Filed May 15, 1958 INVENTOR.

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United States Patent OIL CIRCUIT BREAKERS Haakon Forwald, Ludvika,Sweden, assignor to Allmanna Svenska Elektriska Aktieholaget, Vasteras,Sweden, a corporation of Sweden Filed May 15, 1958, Ser. No. 735,554

Claims priority, application Sweden May 21, 1957 2 Claims. (Cl. 200-150)Oil circuit breakers are known in which a stationary contact is arrangedin a confined extinguishing chamber and a movable contact pin isarranged to traverse an opening in the wall of the extinguishingchamber. In such chambers the gas pressure is increased with increasinginterrupted current. As the gas pressure at opening of the breaking gapacts on the movable contact in the same direction as the force exertedfrom the operating mechanism of the circuit breaker, the speed of thecontact will increase with increasing current. Attempts have been madeto avoid this disadvantage by providing a cylindrical space in themovable contact, which space at one end is closed by a stationary pistonand at the other end is in communication with the extinguishing chamberby a central channel. As the pressure in the extinguishing chamber istransmitted through the said central channel to the cylindrical space ofthe movable contact, a force is attained that actuates the movablecontact in the direction towards the stationary contact. If the innerdiameter of the cylindrical space is chosen equal to the area of thecontact pin at the opening of the extinguishing chamber, a practicallycomplete equalization of the forces generated by the pressure in theextinguishing chamber and actuating the pin is attained. The speed ofthe contacts may then be made independent of the interrupted current.The flow of oil into the extinguishing chamber is, however, combinedwith an increase of the gas volume and thus of the pressure in theextinguishing chamber, which lowers the breaking ability and may causethe chamber to burst.

The present invention concerns an oil circuit breaker with a stationarycontact, arranged in an extinguishing chamber, and a movable contacttraversing an opening in the wall of the extinguishing chamber and beingprovided with a cylindrical space, which is closed in one end by astationary piston. The circuit breaker is chiefly characterised in thatthe part of the movable contact projecitng into the extinguishingchamber is provided with at least one channel which allows the developedgases to escape from the extinguishing chamber, and at least one channelby which the inner space of the extinguishing chamber is incommunication with the closed cylindrical space of the movable contact.The movable contact may suitably be provided with a central channel forthe escape of the breaking gases, which channel is surrounded by aplurality of channels forming a communication between the extinguishingchamber and the above mentioned space in the movable contact.

By the invention a circuit breaker with extremely good breaking featuresis attained, which has been reached by a design allowing the speed ofthe movable contact with an outlet opening for the breaking gases to beinde- Patented Aug. 9, 1960 pendent of the pressure in the extinguishingchamber and thus also independent of the interrupted current.

On the accompanying drawing a form of the invention is shown. Fig. 1shows an extinguishing chamber arranged in an oil container and acontact projecting into said extinguishing chamber. Fig. 2 is a sectionof the movable contact along the line AA. The section through themovable contact in Fig. l is taken along the line BB, as shown in Fig.2. In the figures 1 designates a container partly filled with oil. Atthe bottom 2 of the container an extinguishing chamber 3 of insulatingmaterial is attached. In the lower part of the extinguishing chamber 3the stationary contact of the breaking gap is arranged. This contains ayieldably attached contact block 4, which is actuated by the spring 5 inv the direction towards a locking ring 6. The extinguishing chamber 3 isin its upper part provided with an opening 7, through which the movablecontact 8 of the circuit breaker traverses. The movable contact is inits upper part provided with a cylindrical space 9, which in its upperpart is closed by a stationary piston 10 and which is in communicationwith the space 12 in the extinguishing chamber 3 through channels 11.The movable contact is in its lower part also provided with a centralchannel 13, by which the space 12 communicates with the space 14 outsideof the extinguishing chamber. Breaking gases developed in theextinguishing chamber can escape through this channel. The movablecontact 8 is by means of two rods 16 pivoted on the taps 15 joined withan operating mechanism not shown on the figure. 17 is an arc formedbetween the contacts of the circuit breaker.

I claim as my invention:

1. An oil circuit breaker comprising an oil container, an extinguishingchamber located inside said container and having an opening throughwhich it communicates wth the container, a first stationary contactlocated inside I said chamber, a second contact movable in saidcontainer in the direction of its own longitudinal axis, one end of saidsecond contact being arranged to close said opening and to project intothe chamber, a said second contact having space in the other endotherof, a stationary piston closing one end of said space, the spacebeing decreased during opening movement of the second contact, thecross-section of the piston being substantially equal to thecross-sectional area of said opening whereby the forces generated by thepressure in said chamber and actuating the second contact aresubstantially equalized and the speed of the contacts is independent ofthe current, and the second contact having at least one separateequalizing channel connecting said chamber with said space and at leastone separate escape channel to connect said chamber with said containerwhen the second contact extends into the chamber.

2. An oil circuit breaker according to claim 1, in which the said escapechannel is centrally located in the second contact and is surrounded bya number of equalizing channels providing communication between saidchamber and said space.

References Cited in the file of this patent FOREIGN PATENTS 674,705Germany Apr. 19, 1939 723,208 Germany July 31, 1942 801,759 France May23, 1936

